Alternating current control system utilizing saturable reactor for regulation



Dec. 14, 1954 EBALL ETAL 2 697 200 ALTERNATING ammu- CONTROL SYSTEM UTILIZING SATURABLE REACTOR FOR REGULATION Filed Jan. 25, 1952 Y 2 sheets-sheet 1 I Dec. 14, 1954 AL 2,69 7,200

H. E. BALL ET ALTERNATING CURRENT CONTROL SYSTEM UTILIZING SATURABLE REACTOR FOR REGULATION Filed Jan. 23, 1952 2 Sheets-Sheet 2 SATURATING cmcurr RHEOSTAT POSITION. MIN. CENTER MIAX.

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' 5o OF MAXIMUM CURRENT United States Patent Hugh E. Bali, Lakewood, Ohio, and Eric Pell, Shorewood, is., assignors to Cutler-Hammer, Inc., Milwaukee, is., a corporation of Delaware Application January 23, 1952, Serial No.

11 Claims. (Cl. 323-60) current supplied welders.

range of adjustment.

primary object of the present invention is to provide an alternating current working load.

Other objects and advantages of the invention will hereinafter appear.

accompanying drawings illustrate a preferred embodiment of the invention which will be hereinafter described in detail, it being understood that the embodiment illustrated is susceptible of modification in respect of various details without departing from the appended claims.

In the drawings:

Figure 1 is a diagrammatic showing of an alternating current control system constructed in accordance with the invention and and graph depicting certain operating charactenstics obtainable with the system of Fig. 1.

' out our invention,

operable to ch of the alternating current windings different voltage taps of the autotransformer.

Office we provide a corresponding change in the amount of fixed resistance in the D. C. saturating circuit of the reactor. In other words, a preselected amount of fixed resistance in the D. C. saturating circuit is provided for each different tap connection of the autotransformer. By so doing, minimum transformer. saturating circuit of the reactor, proportionality between rheostat position and the alternating current would be limited to a single A. C. voltage with As 1s well known, any inductance device exhibits a time lag in changing its flux from one value to another. Therefore before connecting the A. C reactor to the More particularly, a source of alternating current is afby supply lines L and L tapped winding autotransformer 5 has its left-hand end terminal 5 connected to supply line L and is connected through a terminal 5 adjacent its right-hand end to supply line L Winding 5 is provided with voltage tap contacts 5 5 5 5 5 and 5 The portion of winding 5 between terminal 5 and tap contact 5 constitutes an overhanging section affording a voltage at Contact member 6 is electrically connected to the upper ends of A. C. windings 8 and 8 of a saturable reactor 8. Windings 8 and 8 are respectively wound on the outer legs of a three-legged core 8 of the reactor and of contacts WC is connected in series with th welding transformer 10 to supply line Transformer 10 is provided with a secondary winding 10 which is connected to the welding electrodes 11 and 12 of a resistance seam welder operating on work pieces 13 and 14. The resistor 9 is connected to the right-hand contact of normally open contacts DLC of an electroresponsive switch DLC. The left-hand contact of contacts DLC is connected to supply line L transformer 15 has a primary winding 15 connected across lines L and L and a secondary Winding 15 connected to the A. C. terminals 16 and 16 of ll-wave, bridge type rectifier 16. D. C. terminal 16 of rectifier 16 is connected through a conductor 17 to the series connected resistors 0, 21 and sistor 18 is connected at its left-hand end to mutating contact 23. The points common between resistors 18 and 19, 19 and 20, 20 and 21, and 21 and 22 are connected to commutating contacts 24, 25, 26

and 27, respectively. The right-hand end of resistor 22 is connected to commutating contact 28. Associated with the contacts 23 to 28 is a slidable contactor 29 mechanically coupled to, but electrically insulated from contactor 7, and a stationary contact member 30. Contact member 30 is connected to the upper end of the D. C. saturating winding 8 of reactor 8. The upper and lower ends of winding 8 are interconnected through a discharge resistor 3 The D. C. terminal 16 of rectifier 16 is connected to the upper end terminal of a resistance element of a potentiometer rheostat 32 which is part of a compound rheostat set 32. The lower terminal of the resistance element of rheostat 32 is connected to conductor 17 in series with a resistor 33. The adjusting element of rheostat 32%- is mechanically coupled to the adjusting element of a rheostat 32 for concurrent adjustment therewith, and is electrically connected to the lower terminal of the resistance element of rheostat 32" The adjusting element of rheostat 32? is electrically connected to the point common to the lower end of winding 8? of reactor 8 and resistor 31.

Rheostat set 32 is of the type disclosed in the aforementioned Pell application, having the resistance elements of rheostats 32 and 32 complementally formed so that for any positioning of the adjusting elements the equivalent resistance of the rheostat set in the circuit aforedescribed will be constant. Reference should be made to the aforementioned application for a more complete understanding of the design and electrical characteristics of rheostat set 32.

Switch WC has one end of its operating winding WC connected to supply line L at the other end thereof connectable to supply line L through normally closed auxiliary contacts DCL of switch DLC and normally open contacts W% of a relay W. A normally open, momentary type switch 34 is connected to line L and is connected through normally closed contacts of switch WC and operating winding DLT of a relay DLT to line L Relay DLT is provided with normally open contacts DLT? which are connected through the left-hand contacts thereof to the point common to the right-hand contact of contacts WC3 of switch WC and operating winding DLT Contacts DLT are connected through the right-hand contact thereof and normally closed contacts DLT and operating winding DLRl of a relay DLR to line L2. Contacts DLT are provided with a time delay device DLT aflording a predetermined delay in opening of contacts DLT following energization of op-. erating winding DLT One end of operating winding DLC of switch DLC is connected to line L? and'its other end is connectable to line L through normally open contacts DLR? of relay DLLR. Relay W has an operating winding W connecte at one end to line L? and has its other end connectable to line L through a normally closed switch 315, normally open auxiliary contacts DLC of switch DLC, contact WC of switch WC and switch 34. Normally open contacts W of relay W provide a maintaining circuit for the operating winding W? through switch 35, following initial energization of winding W and also, provides a maintaining circuit for winding DLT of relay DLT through contacts DLCt whenever they latter are closed,

It will be noted that the voltage tap. contacts 5 to. 5 of autotransformer 5 are alined respectively with the commutating contacts 23 to 28 of the series connected resistors 18 through 22, and that contactor 7 and contactor 29 are slidable on their respective contactmem; bers 6 and M. to simultaneously engage respective alined pairs of voltage tap contacts and cornrnutating contacts, Thus, whenever a voltage provided by a particular voltage tap of autotransformer 5 is selected, a certain pre: selected value of fixed resistance will be effectively connected in the D. C. saturating circuit of reactor 8. As will be appreciated, various other arrangements can be used in place of the voltage tap and resistance com rm a ng ap c nging arr g m n d p d. and. i esired remotely controlled motor driven means can be employed.

With contactors 7 and 2 9 in the position depicted in Fig. 1 voltage tap 5? of autotransformer 5 will be in circuit with the A C, windings of reactor 8,, and resistors 19. ro ll; b ect e y n e. D- Q a u ati ci uit o actor t. be; as umed tha th windings are connected in circuit with winding 10 of welding transformer 16 as by closure of contacts WC of switch WC (contacts 'DLC of switch Then with the value of fixed resistance in the D. C. saturating circuit afforded by resistors 19 through 22, the alternating current supplied to winding 10 can be adjusted throughout a range depicted by the solid line ortion of .curve E in Fig. 2 .by adjustment of rheostat set 32 throughout its range of adjustment. It will be noted that the change in value of A. C. current is substantially directly proportional to change in setting of rheostat se The solid portion .of curve D depicts the rant-5. of possible adiu'stment of A. C. currentwhen ..contactors 7 and 29 are in engagement with tap contact 5 and comt ns co ta t respec vely. the solid portion f curve F the range of possible adjustment of A. C. current when contactors 7 and '29 are in engagement with tap contacts 5 and commutating contact 2., respectively, and the solid portions of curve G the range of possible adjustment when contactors '7 and 29 are in engagement with tap contact 5 and commutat'ng contact 25, respectively. Similarly, the solid portion of curve H depicts the range of possible adjustment .of A. C. current while contactors 7 and 29 are in engagement with tap contact 5 and commutating contact 2'7, respectively, and the solid porcon.-

tion of curve I the range of possible adjustment with tactors 7 and 29 in engagement with tap contact 5 and commutating contact '28, respectively. As previously mentioned in connection with curve D, such range of adjustments depicted by the curves D, F, G, H and J is obtained with adjustment of rheostat set 32 through.- out its range of adjustment.

As a practical consideration in the operation of scam welders it is desirable to keep a high overall power factor of the A. C. circuit and the region above the broken line curve X in Fig. 2 indicates a power factor of 70-88 per cent. Thus, with suitable choice of a voltage tap on autotransformer 5 and suitable adjustment of rheostat set 32 it is possible to provide the desired value of cur: rent in the A. C. circuit while maintaining the overall power factor of such A. C. circuit in such region, and still permit adjustment of the value of the A. cur rent over a wide range.

Adjustments of contactors 7 and 29 to the various associated voltage tap co tacts and commutating contacts is of course done with the A. C. windings of reactor 8 disconnected from the load. As aforeindicated, it is a feature of our invention that the A. C. windings are initially connected to a dummy load for a pred termined interval prior to connection to the working load as will now be described in detail.

Upon momentary closure of switch 34 current flows from line Ll through switch 34, the then closed contacts WC of switch WC and the operating winding DLT of relay DLT to line U. Contacts DLT of relay DLT immediately close, and an energizing circuit is corn-. pleted through contacts DLTZ, the closed contacts DLT and the operating winding DLR of relay DLR to line L Consequently, contacts DLR3 close to complete an energizing circuit for operating winding DLC of switch DLC across lines L and L Contacts DLC and DLC thereupon close and contacts DLC open.

Closure of contacts DLC provides connection of the lower ends of A. Owindings 8 and 8 of reactor 9; to line L in series with dummy load resistor 9. Closure of contact DLC completes an energizing circuit for the operating winding W of relay W, from line L through switch 34, the closed contacts W0 of relay WC, switch 35 and operating winding W of relay W to line L Contacts W and W t relay W thereupon close. Closure of contacts W provides a maintaining circuit for winding W2 o re y W and. he W ndi g DLT of relay L through e. h losed c nta ts D Qt lay LC- Atter a predetermined interval, as determined by the time delay device DLT con ac s DLT open, her by n rrupt n e n izin circui o Windin DLR Qt ay D C nsequ n y contact DLR? pe terrupting the n i i c t r Wi ding. DLC 0t Asv a ult con c s. DLC an DLC. p. contacts DLC,2 close. An energizing circuit for operating Winding W o re a WC? s here y c mpleted. from line L hrough he he cl ed. c ntac s W of elay W. t e c o e c t ct LC a dv w nd ng WC? o ne L Co ts W h teunq clo e whi contact on n- The opening of contacts DLC1 interrupts the connection of A. C. Winding 8 and 8 dummy load resistor 9 to line L and the closing of contacts WC connects these windings in series with the primary winding 10" of welding transformer 10 to line of reactor 8 through circuit withsaid saturating winding the alternating voltage selected for of said resistors in in accordance with said A. C. windings.

6. The combination with a translating device to be Opening of contacts WC insures deenergization of 5 supplied with regulable alternating current, of a saturable winding DLT of relay DLT in the event that switch 34 reactor, means for connecting the A. windings of is maintained closed or reoperate said reactor in circuit with said translating device, means When it is desired to stop the flow of current through including a tapped autotransformer providing a plurality winding of transformer 10, switch 35 is opened, thereof different alternating voltages, a plurality of resistors y interrupting the energizing circuit for winding W 10 having different ohmic values, means for selectively conof relay W As a result contacts W and W open. Opennecting said A. C. windings to different taps of said autoing of contact W interrupts the energizing circuit for transformer and simultaneously effecting series connecwinding WC of relay WC and consequently contacts tion of preselected ones of said resistors in circuit with WC open and contacts WC close. Opening of conthe saturating winding of said reactor in accordance with tacts W interrupts the maintaining circuit for winding t e alternating voltage selected for said A C windings W of relay W. and means including a compound type rheostat in circuit We claim: wit said saturating winding for supplying the latter with 1. In an alternating current regulating system, in comadjustable direct current, said rheostat comprising sepbination means affording a source of a plurality of arate rheostat resistors and individual adjusting elements different alternating voltage values, a saturable reactor, for the respective rheostat resistors interconnected for means for supplying the saturating winding of said ree ecting adjustments of said rheostat resistors simulactor with adjustable direct current, resistance means, taneously, one of said rheostat resistors and its ad ustin and means for selectively connecting the A C windings element affording a potentiometer type rheostat and the of said reactor to the different values of alternating voltother rheostat resistor being series related to said one of age of said source and simultaneously effecting connecsaid rheostat resistors selectable by the adjusting element tion of preselected amounts of said resistance means in ereof and said other of said rheostat resistors being series with said saturating winding in accordance with appropriately tapered so that for all settings of its adthe alternating voltage value selected for said A. C. usting element and all amounts of fixe resistance in windings. said saturating circuit of said reactor said compound 2. In an alternating current regulating system, in comrheostat will have constant equivalent resistance. bination, means including a transformer winding having 7. in combination, a Welding transtoimer, a saturable a plurality of voltage taps providing a correspondin numreactor, means for connecting the A C. windings of said er of different alternating voltages a saturable reactor reactor in circuit with t e primary Winding of said weld means including rheostat means for supplying the saturating transformer, means including a tapped autotransing Winding of said reactor with ad ustable direct current, 5 ioimer providing a plurality of different alternating voltresistance mean and means for selectively connecting ages, means including rheostat means for supplying the the A. C. windings of said reactor to the different voltsaturating winding of said reactor with ad ustable direct age taps of said transformer windings and simultaneously current, a plurality of resistors having different ohmic e ecting connection of preselected amounts of said revalues, and means for selectively connecting said A C sistance means in series with said saturating winding in windings to the different taps of said autotransformer and accordance with the alternating voltage selected for said simultaneously effecting series connection of preselected A C. windings ones of said resistors in circuit with said saturating wind- 3. In an alternating current regulating system, in coming in accordance with the alternating voltage selected bination, means including a transformer winding having for said A. C. windings. a plurality of voltage taps providing a corresponding 8. The combination with a translating device to be number of different alternating voltages, a saturable resupplied with regulable alternating current and a source actor, means including rheostat means for supplying the of alternating voltage, of inductive current regulating saturating winding of said reactor with ad ustable direct means, means affording connection of said regulating current a plurality of resistors having different resistance means in circuit with said source, means constituting a values, and means for selectively connecting the A C. dummy load and means including control means operable windings of said reactor to the different voltage taps of to connect said regulating means in circuit with said said transformer winding and simultaneously effecting dummy load for a predetermined interval and thereafter series connection of preselected ones of said resistors in connect said regulating means in circuit with said transcircuit \VlLh said saturating winding in accordance with ating device, to insure magnetic stabilization of said the alternating voltage selected for said A C windings. regulating means prior to its connection in circuit with The combination with a translating device to be said translating device. supplied with regulable alternating current, of a saturable 9. The combination with a translating device to be reactor, means for connecting the A. C. Win ings of said supplied with regulable alternating current and a source reactor in circuit with said translating device means inof alternating voltage, of a saturable reactor, means cluding a tapped autotransformer providing a plurality of affording connection of the A. C windings of said reactor different alternating voltages, means including rheostat in circuit with said source, means including adjustable means for supplying the saturating winding of said reactor means for supplying the saturating winding of said rewit ad ustable direct current, a plurality of resistors actor with adjustable current, means constituting a dummy having different resistance values, and means for selecload, and means including control means operable to tively connecting said A C. windings to the different taps initially connect said A C windings in circuit with said of said autotransformer and simultaneously effecting series dummy load for a predetermined interval and thereafter connection of preselected ones of said resistors in circuit connect said A. C windings in circuit with said transwith said saturating winding in accordance with the lating device, to insure magnetic stabilization of said alternating voltage selected for said A. C. windings. reactor prior to its connection in circuit with said trans- 5. The combination with a translating device to be latiiig device. supplied with regulable alternating current, of a saturable 10. The combination with a translating device to be reactor, means for connecting the A. C. windings of said supplied with regulable alternating current and a source reactor in circuit with said translating device, means of alternating voltage, ofasaturable reactor, means affordincluding a tapped autotransformer providing a plurality ing connection of the A. C. windings in circuit with said 0 different alternating voltages, means including rheostat source, means including adjustable means for supplying means for supplying the saturating winding of said rethe saturating winding of said reactor with adjustable actor with adjustable direct current a plurality of series direct current, means constituting a dummy load an connected resistors of different iesistance values a pluelectroresponsive switch energizable to connect said A C rality of commutating contacts in circuit with said rewindings in circuit with the dummy load, a second elecsistors and exceeding by one the number of resistors, troresponsive switch energizable to connect said A C means operable to selectively connect the different voltwindings in circuit with said translating device, a rela age taps of said autotransformer in circuit with said A C having time delay means, said relay being energizable windings of said reactor, and means operable by the last to complete an energizing circuit for the first mentioned mentioned means for effecting through engagement with switch and following a predetermined interval acting to said commutating contacts connection of preselected ones interrupt the energizing circuit for said first mentioned switch and complete an energizing circuit for said second switch, and means operable to energize and deenergize said relay.

'11. In combination, a welding transformer, means including a tapped autotransformer providing a source of a plurality of different alternating voltages, a saturable reactor, a plurality of resistors having different resistance values, means for selectively connecting the A. C. Wind ings to difierent taps of said autotransforrner and simultaneously effecting series connection of preselected ones of said resistors in circuit with the saturating winding of accordance with the alternating voltage selected for said A. C. windings, means including rheostat means in circuit with said saturating winding for cuit with said transformer.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,820,242 Niemann et a1 Aug. 25, 1931 2,440,319 Wickerham Apr. 27, 1948 2,547,615 Bedford Apr. 3, 1951 

